Conventional electronic chassis or modules used for high-speed computer applications typically are metallic boxes. Numerous circuit boards (also known as application cards) are slid into the electronic chassis along card guide assemblies. Each application card typically includes a large number of electronic components. As a result, these application cards generate a tremendous amount of heat, which must be removed from the chassis to protect the various electronic components within the chassis.
The requisite cooling of electronic devices is typically accomplished by ambient or forced convection cooling. When forced convection cooling is used, a volume of air is directed past the electronic devices either by suction or by pressure. In the chassis for such devices, it is known to orient the cards parallel to the direction of air flow to enhance cooling. Conventional fans have been used to bring cooling air into the chassis and, at the same time, to exhaust heated air from the chassis.
More specifically, various attempts have been made to reduce the temperature within an electronic chassis by providing a fan tray assembly, which includes one or more conventional fans. The fan tray assembly is often housed within the chassis. Cool air is circulated through the chassis between the card guide assemblies, and the heated air is exhausted from the chassis. Such conventional fan tray assemblies have several drawbacks.
First, electronic chassis typically have strict dimensional requirements, rendering the size and orientation of the fans critical in the attempt to maximize the amount of air flow through the chassis. Fan tray assemblies housed within the chassis occupy valuable space. This drawback is exacerbated because, in an effort to increase the output of the cooling ability of the fans, which is necessary to prevent overheating of the electronic components within the chassis, most conventional designs have relied on the premise that bigger is better and have increased the size of the fans themselves. This premise results in an increase in the space required within the chassis for the fan tray assembly, which is typically not feasible. The premise also creates other problems, including an increase in the weight of the chassis beyond acceptable limits, an increase in the number of parts, and an increase in the cost of production.
Some of the drawbacks faced when the fan tray assembly is housed within the chassis can be avoided by designing the fan tray so that it can be removed from and inserted into the chassis or module. U.S. Pat. No. 6,388,880 issued to EI-Ghobashy et al. discloses a removable fan tray assembly with locking features. Specifically, slam latches are mounted in a front panel and hold the fan tray securely in the chassis providing a gripping point for withdrawing the fan tray from its position in the chassis. As shown in FIG. 4 of the patent, tongues of the slam latches engage cutouts in the side panels to hold the fan tray in place. The slam latches can be displaced toward the center of the fan tray, withdrawing the tongues from the cutouts. The signal cable connector and power connector engage the fan tray connectors by passing through cutouts in the chassis and fan tray. Therefore, in order to slidably remove the fan tray from the chassis along the flanges, both the signal cable and the power connector must be unplugged from their respective connectors. Although this feature assures that the fan tray is not displaced without first unplugging the signal and power cables, it adds complexity and a number of steps to the process of inserting or removing the fan tray assembly.
Some of the drawbacks faced when the fan tray assembly is housed within the chassis can be avoided by mounting the fan tray to, rather than within, the chassis or module. If they are removably attached, externally mounted fan tray assemblies also provide another advantage: they facilitate access to the electronic components within the chassis. In the ever-advancing field of computer equipment, the need to upgrade, replace, or service electronic components is more prevalent than ever. Many different solutions are known for installing new components or removing existing components to facilitate replacing or servicing components.
The goal of externally mounting a fan tray assembly to a chassis in a removable manner is not easily achieved. Not all devices or methods allow technicians to perform the work efficiently, quickly, and reliably. This disadvantage is particularly true for components that require fasteners such as screws for mounting purposes, or those that require complex latching or retention mechanisms for enhanced retention capability.
One example of a known solution is a squeezable latch. The latch mounts to a first component and has two engagement points that are spaced apart on opposite sides of the component. The engagement points engage a retention mechanism that is mounted to a second component. Depending upon the sizes of the respective components, a technician can operate the latch with one hand by squeezing the latch at the engagement points. Larger components require the technician to use two hands, however, to operate the latch. Moreover, this latch can be mishandled by the technician and result in uneven insertion or extraction of the first component. If the force exerted on the component is uneven, it may be “rocked” into or out of place, thereby increasing the probability for damage.
Another known example is the cam-type lever. If the device is single-sided, only one side of the component is clamped which can result in uneven insertion or extraction. Dual cam devices are workable, but they have more parts and require the technician to use both hands. There are other types of manual release mechanisms, but many of these are unnecessarily complex and require multiple, simultaneous operations to be performed by the technician to achieve insertion or extraction. These operations also typically cause the component to be rocked out of place and may cause damage.
U.S. Pat. No. 6,236,573, issued to Gundlach et al., illustrates a conventional apparatus and method for manipulation of latching, pluggable electronic components. A computer processor cartridge is connected to a socket on a motherboard. The cartridge has a detachable bracket that secures it to a retention mechanism mounted to the board. The bracket is formed from flexible plastic and has a handle with downward-depending arms on each end. Each arm has a tooth on its outer surface. The retention mechanism has a base with a pair of upright support posts on its ends. Each post has a hole in its side for receiving the teeth on the bracket. The cartridge and bracket assembly is installed in the retention mechanism by pushing down on the handle such that the lower end of the assembly seats between the support posts. When the teeth engage the holes in the support posts, the assembly is locked in place and the cartridge is connected to the socket. The assembly is disconnected by pulling up on the handle. The plastic bracket elastically flexes so that the arms pivot the teeth out of the holes. Additional upward force on the handle pulls the cartridge out of the socket so that the assembly can be completely removed from the retention mechanism.
Unisys Corporation markets a fan tray assembly specifically directed to the goal of externally mounting a fan tray assembly to a chassis in a removable manner. This assembly has two pull handles disposed on each side of the fan tray. The symmetrical pull handles facilitate manipulation of the fan tray. Two hands are required of the technician, however, to manipulate the fan tray. In addition, careful alignment between the fan tray assembly and the chassis is required along both sides as the fan tray and chassis are engaged and disengaged.
To overcome the shortcomings of existing fan tray assemblies used to cool electronic components housed within a module, a new fan tray assembly is provided. An overall object of the present invention is to provide an improved fan tray assembly. Yet other overall objects are to maximize the flow of air through the module, reduce air diversion from the cooling air flow, and minimize the need for blocking structures in the area to be cooled. A more specific object of the present invention is to accommodate fully the space allotted to the fan trays by the module.
Another object is to render the fan tray assembly “hot plug able” in that the fan assembly can be removed and replaced while the electronic components operate. It is still another object of the present invention to facilitate easy and fast removal and replacement of the fan trays. A related object is to eliminate some of the components required by conventional fan assemblies, including separate tools for removal and replacement. Still another related object is to automatically align the fan tray connector with the module receptacle. An additional object is to incorporate into the fan assembly shielding against electromagnetic interference (EMI) radiation that tends to leak from the electronic components.